The frequency and/ or duration of naps rapidly increases among those with mild cognitive impairment, a precursor of dementia. The corresponding study was published in Alzheimer's and Dementia.
Some suggest that daytime napping among older people can compensate for a poor night of sleep. However, others suggest that dementia may affect the wake-promoting neurons in key areas of the brain, and that excessive daytime napping may thus occur independently of nighttime sleep quality among those with pre-dementia or dementia.
In the present study, the researchers examined longitudinal data from 1401 older adults at an average age of 81 taken over 14 years. Each wore a watch-like activity tracker continuously for up to 14 days each year and underwent several neurological tests. At the start of the study, 75.7% f the participants were not cognitively impaired, while 19.5% had mild cognitive impairment and 4.1% had Alzheimer's disease.
After analyzing the data, the researchers found that while older adults tend to nap longer and more frequently as they age, the progression of Alzheimer's dementia accelerates this change by more than doubling annual increases in nap duration and frequency.
The researchers noted that 24% of those who did not have cognitive impairment at the start of the study developed Alzheimer's six years later. When comparing this sample to those whose cognition remained stable, they found that participants who napped for more than an hour per day had a 40% higher risk of developing Alzhiemer's than those who napped for less than an hour per day.
They further found that participants who napped at least once per day on average were 40% more likely to develop Alzheimer's than those who napped less than once per day.
While the researchers say they do not have enough evidence to draw conclusions about a causal relationship, they say that the changes may be explained as those with Alzheimer's disease have fewer wake-promoting neurons in three brain regions and that these changes may be linked to buildups of tau protein- a biomarker or Alzheimer's disease.
"I don't think we have enough evidence to draw conclusions about a causal relationship, that it's the napping itself that caused cognitive aging, but excessive daytime napping might be a signal of accelerated aging or cognitive aging process," said Yue Leng, MD, Ph.D., co-senior author of the study.
"It would be very interesting for future studies to explore whether intervention of naps may help slow down age-related cognitive decline," she added.
Sources: Alzheimer's and Dementia, Science Daily
